Process and apparatus for removing liquid from a moving web of paper and the like



May 7, 1968 H. w. CLARK 3,381,607

PROCESS AND APPARATUS FOR REMOVING LIQUID FROM A MOVING WEB OF PAPER AND THE LIKE Filed Aug. 1, 1966 flfi/ofi AFT MP5 20 l m/1V F044 l6 foo 1/50 Razz c TOE p 70/? faaygp FELT /0-; mp5? WEB/J I /0 6(00 v Pa ,4 Far /0 P425? Was Q 4 INVENTOR.

HORACEW. CLARK United States Patent 6 3,381,607 PROCESS AND APPARATUS FOR REMOVING LIQUID FROM A MUVING WEB OF PAPER AND THE LIKE Horace W. Clark, Chillicothe, Ohio, assignor to The Mead Corporation, Dayton, Ohio, a corporation of Ohio Filed Aug. 1, 1966, Ser. No. 569,458 9 Claims. (Cl. 100-37) The present invention relates to improved methods and apparatus for drying moving webs and, more particularly, to. improved methods and means for removing liquid from a moving liquid-containing web.

The invention is particularly useful in connection with the removal of water from moving webs of paper, pulp, paperboard or the like. In the manufacture of such webs, a web is formed from a slurry of fiber material on a wire or other forming element of a paper machine which readily drains off a substantial amount of the water portion of the slurry. The newly formed web, still containing considerable water, is transferred to a supporting felt on which it is carried through a series of pressing stations which comprise cooperating rolls that function in a manner similar to wringer rolls to squeeze water from the web as it passes through a pressure nip between such rolls. When solid rolls are employed for such purpose, the water is squeezed from the web through the felt onto the surface of the lowermost roll and drains from or is removed from such surface. Presses utilizing solid rolls are generally referred to as plain presses to distinguish them from vacuum presses in which one or both rolls may be hollow and provided with a perforated shell and a suction chamber which acts in the nip region to remove the Water from the perforated roll surface. In vacuum presses, water squeezed from the web by the press rolls is drawn through the felt into the interior of the hollow perforated shell from which the water is removed either by being sucked into the suction chamber or by being thrown outwardly into collecting pans. Either plain or suction presses have been, in general, efiective to remove water from a liquid-containing moving web but both of these means and/ or methods are subject to certain limitations and disadvantages.

In seeking to improve the operation of plain presses by increasing water removal capacity and to avoid re-wetting of the web, a prior approach squeezed water from the web through the felt and into a mat or belt which was simultaneously passed with the web and the felt through the nip of a pair of plain press rolls. After passing through the nip, the water is retained temporarily in openings in the mat or belt until it has been separated from the web and the felt and, at a location remote from the nip, the mat or belt is caused to make a sudden and abrupt change in its direction of travel, thus throwing the water from said openings by centrifugal action. However, some water remains in the mat or belt which must be removed therefrom by other means, such as suction, heat or pres sure before the endless mat or belt again contacts the web.

Also, to improve water removal capacity, to avoid rewetting of the web, and to avoid shadow marking and/ or crushing of the web structure, which problems are aggravated by the high nip pressures and the perforated shells used in vacuum presses, another prior approach utilized a grooved press roll to receive water squeezed from the web at the nip and to vent the nip pressure together with a stationary curved sheet member bearing against the grooved roll to provide a pumping action for removal of water from the grooves of the grooved roll. Such arrangement, while efiective at high operating speeds, is ineffective to remove water at low speeds and is subject to serious wear problems when operated at high speeds. Accordingly, it is an object of the present invention to provide an improved means and method for obviating the above mentioned difiiculties.

Another object of the invention is to provide methods and apparatus to more efi'iciently and completely remove liquid from liquid-containing moving webs such as paper, pulp, paper board and the like.

A further object of the invention is to improve the operation of wet presses of a paper machine by provision and utilization of improved apparatus that is mechanically simple, sturdy, reliable, capable of operating over extended periods of time without requiring excessive maintenance or shut down periods for repair or replacement purposes and is effective in the removal of liquid from liquid-containing moving webs at all normally employed speeds.

Still another object of the invention is to provide improved apparatus of low capital cost and of minimum operating and maintenance cost for the removal of liquid from liquid-containing webs moving at all normally employed speeds.

A still further object is to provide methods and apparatus for removing liquid from liquid-containing moving webs which overcome known disadvantages of the prior art methods and apparatus.

In general, the present invention contemplates the employment of surface tension forces for the removal of liquid from the grooves of a grooved press roll and the avoidance of rubbing or frictional contact with said roll. The invention will be better understood and other objects and advantages thereof will become apparent from the following description taken in connection with the accompanying drawings wherein:

FIGURE 1 is a diagrammatic sectional view illustrating apparatus for practicing water removal method of the prior art;

FIGURE 2 is a diagrammatic sectional view illustrating one embodiment of apparatus for carrying out the method of the invention;

FIGURE 3 is a diagrammatic sectional view illustrating a modification of the embodiment of FIGURE 2; and

FIGURE 4 is a diagrammatic sectional view illustrating a still further modification.

Referring to FIGURE 1, a moving paper Web 10 and felt 11 pass together through the nip of a pair of press rolls 12, 13 which rotate in the direction indicated by the arrows. As illustrated, roll 12 is a plain roll and roll 13 is a grooved roll. The pressure developed at the nip between rolls 12, 13 squeezes water from paper web 10 through felt 11 and into grooves 14 in the surface of roll 13. As roll 13 continues to rotate in the direction indicated by the arrow, such water is retained within grooves 14 and is carried thereby upwardly and away from the nip and paper web It and felt 11. A stationary curved sheet member 15 is disposed in rubbing contact substantially throughout the entire length of the surface of roll 13 and thus provides a pumping action which lifts water from within grooves 14 and deposits it on the surface of roll 13. At a location above the line of contact between member 15 and roll 13, a doctor 16 is provided to remove such water then on the surface of roll 13. Water removed by doctor 16 is collected in a pan 17 interposed between doctor 16 and felt 11. As noted heretofore, such an arrangement is ineffective at low speeds and is subject to objectionable wear of member 15 at high speeds, thus requiring frequent interruptions in operation in order to repair or replace the worn member.

As is shown in FIGURES 2 and 3, the present invention embodies apparatus that is generally similar to that of FIGURE 1 in that a web and a felt 11 are passed simultaneously through the nip of a pair of press rolls 12, 13. Roll 13 is a grooved roll having grooves 14 provided in its surface. Although the design and configuration of grooves 14 is somewhat critical in order to provide adequate liquid removal capacity of the liquid to be removed from the liquid-containing web and to insure that such liquid will be retained in the grooves under the influence of surface tension forces for the desired period of time, such design and configuration requirements are known to those skilled in the art and, accordingly, are not set forth herein in detail. Such design and configuration requirements are, for example, set forth in United States Letters Patent No. 3,198,693.

In the embodiments illustrated in FIGURES 24, curved sheet member 15 has been replaced by a plain roll suitably and rotatably supported in a known manner and disposed with the surfaces of rolls 13 and 20 in rolling contact and forming a nip therebetween. With grooves 14 containing liquid and with rolls 13, 2t) rotating as indicated by the arrows, the rolling action of roll 20 lifts the liquid from grooves 14 as they pass through the nip between rolls 13, 2t] and deposits such liquid on the surface of roll 13 on the exit side of the nip. Such liquid is removed from the surface of roll 13 by a doctor 16' spaced from and disposed on the exit side of the nip between rolls 13, 20 and between said nip and the nip between rolls 12, 13.

Operational experience has shown that this method and apparatus for removal of liquid from a moving web is a significant improvement over the prior art method and apparatus illustrated in FIGURE 1 in that the method and apparatus of the present invention substantially eliminates or minimizes wear and consequent repair or replacement problems and is about equally effective from the viewpoint of liquid removal capacity.

Additional improvement is obtained by providing roll 20 with a relatively soft resilient surface 20a, such as rubber or the like, to provide a wider and more uniform nip between rolls 13 and 20. Operational experience indicates that the relative hardness or softness of surface 20a is not particularly critical although a roll surface of a particular hardness or softness may be more eflicient under one set of operating conditions than under another. Similarly, the nip pressure between rolls 13, 26 does not seem to be particularly critical, although a particular nip pressure or loading under one set of operating conditions may be more efiicient than under another. Operational experience has been obtained within a range wherein roll 20 was loaded only by its own weight to loadings in the range between 200250 p.l.i. (pounds linear inch).

Experience has further shown that, as noted heretofore, the action of roll 20 lifts liquid from grooves 14 in roll 13 and deposits such liquid on the surface of roll 13 and that a portion of such liquid may be deposited on the surface of roll 20. Hence, it is desirable to also provide a doctor for the removal of liquid from the surface of roll 20 as well as for roll 13, particularly since it has been found there is a limit to the water removal capacity of the press when no doctor is employed for roll 20.

4 When such limit is reached, grooves 14 remain filled and a pool of liquid forms between rolls 13 and 20.

As illustrated in FIGURE 4, wipe 16" has been replaced by an alternative means for removing liquid from the surface of roll 20. As in the embodiments previously described, web 10 and felt 11 are passed simultaneously through the nip of a pair of cooperating press rolls 12, 13 so that liquid is squeezed from web 10 through an endless felt 11 and into grooves 14 provided in the surface of grooved press roll 13. As the liquid in grooves 14 passes through a second nip between roll 13 and roll 20, the action of roll 20 lifts such liquid from said grooves onto the surface of roll 13, and a portion of such liquid is also deposited onto the surface of roll 20. In this embodiment of the invention, the means for removing such liquid from the surface of roll 20 comprises still another roll 30, which is a plain roll. Roll 30 is also rotatably supported in a known manner and is disposed with surfaces of rolls 20, 30 in rolling contact and forming a nip therebetween. Water on the surface of roll 20 is squeezed therefrom by the action of roll 30 in the region approaching the nip between rolls 20, 30 and falls under the influence of gravity into a collecting pan 31. Pan 31 extends beneath rolls 13, 20 and 30 and the respective nips therebetween and thus receives any liquid that may fall either from said respective nip regions or from the respective surfaces of said rolls. Accordingly, doctor 16' may or may not be provided for removal of water from the surface of roll 13.

While particular embodiments of the invention have been illustrated and described, it will be obvious that various changes and modifications may be made without departing from the invention and it is intended in the appended claims to cover all such changes and modifications that fall within the true spirit and scope of the invention.

What is claimed is:

1. In a process for removing of liquid from a liquidcon-taining moving web of paper and the like wherein said web is passed through a nip of a pair of press rolls at least one of which is a grooved type of roll having sub-surface cavities for the temporary retention of a liquid under the influence of surface tension forces, liquid is transferred from said web into said cavities by rolling pressure from said press rolls and temporarily retained therein after passing through said nip, the improvement which comprises passing said liquid containing cavities through a second nip formed between said grooved roll and a third plain roll,

lifting said liquid from said cavities and depositing it onto the surface of said grooved roll by rolling action of said plain roll, and

thereafter removing said liquid from the surface of said grooved roll.

2. Process according to claim 1 wherein said lifting and depositing step includes the deposition of a portion of said liquid onto the surface of said plain roll.

3. Process according to claim 2 and additionally including the step of removing liquid from the surface of said plain roll.

4. Process according to claim 3 wherein said grooved roll and said third plain roll are resiliently pressed together.

5. Process according to claim 2 and additionally in cluding the step of removing liquid from the surface of said plain roll by rolling pressure applied thereto by a fourth plain roll.

6. In an apparatus for removing liquid from a liquidcontaining moving Web of paper and the like including a pair of cooperating press rolls having a nip therebetween, means for moving said web through said nip and simultaneously transferring liquid from said web into a plurality of subsurface cavities in at least one of said rolls under rolling pressure from said press rolls for temporary re- 5 tention in said cavities after said transfer, the combination comprising means spaced from and at the exit side of said nip for transferring liquid temporarily retained in said cavities onto the surface of said one roll, said means including a third roll rotatably pressed against the surface of said one roll, and

means for removing liquid from the surface of said one roll.

7. Apparatus according to claim 6 and additionally including means for removing liquid from the surface of said third roll.

8. Apparatus according to claim 7 wherein said additional means includes a fourth roll rotatably pressed against the surface of said third roll.

9. Apparatus in accordance with claim 6 wherein the surface of said third roll is of resilient material.

References Cited UNITED STATES PATENTS LOUIS o. MAASSEL, Primary Examiner. 

1. IN A PROCESS FOR REMOVING OF LIQUID FROM A LIQUIDCONTAINING MOVING WEB OF PAPER AND THE LIKE WHEREIN SAID WEB IS PASSED THROUGH A NIP OF A PAIR OF PRESS ROLLS AT LEAST ONE OF WHICH IS A GROOVED TYPE OF ROLL HAVING SUB-SURFACE CAVITIES FOR THE TEMPORARY RETENTION OF A LIQUID UNDER THE INFLUENCE OF SURFACE TENSION FORCES, LIQUID IS TRANSFERRED FROM SAID WEB INTO SAID CAVITIES BY ROLLING PRESSURE FROM SAID PRESS ROLLS AND TEMPORARILY RETAINED THEREIN AFTER PASSING THROUGH SAID NIP, THE IMPROVEMENT WHICH COMPRISES PASSING SAID LIQUID CONTAINING CAVITIES THROUGH A SECOND NIP FORMED BETWEEN SAID GROOVED ROLL AND A THIRD PLAIN ROLL, LIFTING SAID LIQUID FROM SAID CAVITIES AND DEPOSITING IT ONTO THE SURFACE OF SAID GROOVED ROLL BY ROLLING ACTION OF SAID PLAIN ROLL, AND THEREAFTER REMOVING SAID LIQUID FROM THE SURFACE OF SAID GROOVED ROLL. 